1. Field of the Invention 
The present invention concerns data transmission techniques, in particular data transmission techniques in which the transmitted data is structured in blocks known as frames comprising payload data and data referred to herein as auxiliary data enabling frame synchronization of a receiver to a transmitter.
2. Description of the Related Art 
Auxiliary data of the above kind generally includes a synchronization pattern (flag) formed of a predetermined sequence of bits usually placed at the head of the frame.
Because it is necessary to guard against the payload data imitating the synchronization pattern, auxiliary data of the above kind usually further comprises synchronization bits intended to prevent such imitation interleaved with the payload data: if the synchronization pattern is a sequence of eight bits at 0, for example, bits at 1 are inserted every seven bits.
However, inserting auxiliary data of the above kind is clearly to the detriment of the payload data, which therefore raises a problem of frame efficiency, especially if it is required to increase the transmitted payload without increasing the bit rate.